I'm not sure if this is the right forum but does anyone know what Maxson's reference ID is, please? He's gone missing and I need to move him to me so I can speak to him.

In fact, I may not need to. Do I need to complete Liberty Primed to access Blind Betrayal? The Wiki says I only need to complete Outside the wire, which I have, but Maxson's pulled a disappearing act since.

If he is gone from his position on the Prydwen he is probably in his quarters. He moves around abit at some points in the main quest. Yes you need Liberty Prime as far as i remember.

If I'm not siding with the Brotherhood, is there a consequence to my rebuilding Liberty Prime for them? Yes or no, no spoilers, please

Nope.

It helps in the Institute ending.